That sounds like a serious concern that the Canadian legislature should have taken into account before passing the Online News Act.
By imposing fees when a website user posts a link to a news article, the legislature thereby gave the websites a choice: ① Pay the fees, or ② stop doing the behavior that triggers the fees — namely, allowing users to post those links.
In general, when you impose a tax on some action, people do less of that action. People buy fewer cigarettes when the cigarette tax is raised. Raising gasoline taxes leads (eventually) to people opting for more fuel-efficient cars. And if you tax websites for carrying links to news articles, many of those websites will choose to stop doing that.
Federal, provincial, and territorial emergency management agencies have lots of non-social media ways of telling people to get out of Dodge, but for smaller updates on a situation that don't need an alarm going off on everyone's phone in a huge area social media and news are more reliable for reaching a large number of people. People don't check government websites often enough, but they check twitter and Facebook a lot, and it's repeatedly shown to be the method that gets the most attention from affected people.
A lot of these smaller updates are stuff like status of people's homes, updates on the wildfire and suppression efforts, options for evacuees, reminding people to stay out of town, etc.
Actual emergency warnings that need urgent action result in every phone in the region blaring like they're waking the dead. Those do not rely on the benevolence of foreign corporations.